Technical Field
The present invention relates to a clock signal generating apparatus, a method for generating a clock signal, and a non-transitory recording medium storing a program for causing a computer to execute the clock signal generating method.
Description of the Related Art
Electronic devices such as computers include a plurality of circuits such as a central processing unit (CPU), and each circuit operates in accordance with a clock signal (sync signal) that repeatedly oscillates between a high and a low state in a certain cycle. A clock signal is generated by a crystal oscillator that generates a pulse at a certain time interval. All clock signals required by the individual circuits do not have the same frequency. Therefore, a variable frequency generating circuit such as a phase locked loop (PLL) circuit is used to change the frequency of a clock signal generated by a crystal oscillator, thereby generating a clock signal with a frequency required by each circuit.
Because electric current that flows through wiring or the like changes, a clock signal generates electromagnetic interference (EMI) that has such effects as obstructing the operation of an external device. EMI has a peak at a particular frequency, and the above-described effects are caused by a strong electromagnetic wave radiated at that peak.